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Building Technologies
Basic documentation: Communication via the KNX bus
CE1P3127en
HVAC Products
Large plants
30.08.2007
8 Large
plants
8.1
Engineering and commissioning
In large plants, the following points must be observed during the design
engineering and commissioning stages.
For all lines, the distances and line lengths (see section 2.3.1) must be observed. If
the topology exceeds the prescribed limits, then area/line couplers must be used.
A maximum of 64 bus devices may be installed on one line. In systems with more
than 64 bus devices, the bus devices must be distributed to different lines and/or
areas (see section 2.1.2).
When structuring large plants, LTE-compatible area/line couplers are required (see
section 1.4).
For the "KNX – IP network" connection, LTE-compatible IP routers are required
(see section 1.4).
The area/line couplers and IP routers must contain the predefined LTE filter table
(see section 8.2).
Alarm drains should be on the same line or the next higher line in the hierarchy
(see section 8.1.1, example 2). The following are alarm drains:
•
OZW771 central communication unit
•
OZW775 central communication unit
•
RM… controllers with an enabled alarm relay
Devices with room functions should be located on the same line as the devices
with which they exchange data via KNX in LTE mode, for example:
•
Synco QAW740 room unit
Ù
Synco RM… controllers
•
RXB/RXL room controllers
Ù
Synco RMB795 central control unit
•
Synco RM… controllers for room control combinations (see section 9.3)
Only one bus device in the network may be configured as the time master (see
also "Time synchronization" in section 6.1.2).
A search via ACS for devices in all areas and lines only works with correctly
addressed area/line couplers (see section 5.9).
The following "design rules" must be observed when addressing zones:
•
The zone addresses, which can be filtered, are permanently predefined in the
LTE filter table (see section 8.2). For this reason, both the assignment of devices
to areas and lines, and the addressing of the zones must be planned with
extreme care.
•
The data traffic should be kept to the minimum by creating "communication
islands" (see section 1.4).
•
There is a limit to the number of LTE telegrams that can be transmitted via
area/line coupler and IP router (see section 8.2.4).
Large plants
Distances and conductor
lengths
Number of bus devices
Area/line couplers
IP routers
Predefined filter table
Alarm drains
Devices with
room functions
Time master
ACS7… software
Design rules for
zone addressing
